In silver halide color photographic light-sensitive materials, it is well known that a development accelerator or a fogging agent is released from a certain kind of coupler during color development processing. U.S. Pat. No. 4,390,619 and Japanese Patent Application (OPI) Nos. 150845/82 and 50439/84 (British Patent Application No. 2,131,188A) (the term "OPI" as used herein refers to a "published unexamined Japanese patent application") disclose couplers which release fogging agents upon reacting with color developing agent oxidation products and demonstrate the effects to increase contrast or accelerate development brought about by the imagewise release of fogging agents. However, it is believed that these compounds are incapable of releasing a fogging agent in monochromatic development in which monochromatic developing agents, e.g., hydroquinone, methol, 3-pyrazolidone, etc., are used. Therefore, these known compounds cannot be employed in light-sensitive materials which are subjected to monochromatic development requiring high contrast and development acceleration, such as common monochromatic light-sensitive materials, color reversal light-sensitive materials, monochromatic light-sensitive materials for printing, monochromatic light-sensitive materials for X-rays, monochromatic light-sensitive materials having high resolving power, light-sensitive materials for a diffusion transfer process and the like. In order to heighten contrast or accelerate development in monochromatic development, it is desired to develop a compound which imagewise releases a fogging agent through monochromatic development.
Japanese Patent Application (OPI) No. 55332/75 or U.S. Pat. No. 4,435,495 makes some reference to such a compound, but the descriptions therein mainly relate to development inhibitor releasing compounds. There is no description therein as to either specific examples of such a compound or specific effects thereof.